Multiple Rapid Charging / Charging concerns & why I wouldn’t buy a 39kWh Kona Electric

Not my finest video creation for sure. I’ve really disliked making this video from start to end.

The idea was simple, three rapid charges and some quick driving but I wasn’t to know my opinion of the car would dramatically change.

So much of the footage I shot became redundant and Inappropriate once I analysed the data. The car seems to charge slower than I expected and potentially had issues charging from cold. The BMS becomes active at various times without a consistent pattern.

Compared to the 64kwh version the 39kwh is half the car when you consider it’s limited range in worst case scenarios and slower charging performance.

Remember this is my opinion only and I’ve been spoilt with the 64kwh version.

With so much secrecy from Hyundai about what the BMS is actually doing, we simply can’t fully understand the cars abilities in respect to charging and hence it’s sadly easy to draw conclusions from tests such as this. Ideally, such tests would be repeated over multiple times to prove results and again varying parameters to learn more.

The charging time of 57 minutes seemed accurate for the 20% to 80% charge but sadly 6% to 80% wasn’t so swift.

Does the 39kwh Kona have issues charging from cold? Why does the BMS come on when the battery is cold? Why was charging limited to 14kw from cold in my final test? All unanswered I’m afraid.

UK Kona Electric specs:

Facebook Page: Page:


Patreon link:

Twitter: @KonaElectric

  • If a 39Kwh capacity battery is charged at the same rate as a 64Kwh capacity battery, it will be being charged at nearly twice the power of the larger battery. This is why the 39KWh battery will have lower KWh charge rates.

  • My car tapers a lot when charging on DC. But there seems to be a correlation between State of Charge (what’s in the battery) and the Charge Rate (in kWs). In the 38kWh Kona it seems to be about 90. So take the SoC away from 90 and it gives you a rough expected Charge Rate. eg if battery is at 70%, Charge should be about 20 kW. (90-70=20). At 40% SoC, Charge Rate should be about 50kW (90-40=50). It’s very wet finger but seems to work. Might be worth seeing if there is a similar correlation in your 64 kWh Kona. (NB Doesn’t seem to work at the very bottom 15% or less, or very top of SoC, 85% or above)

  • In the same way that high battery temperature reduces charge rate, low battery temperature will certainly result in a low charge rate.
    Presumably the BMS is programmed with charging rates related to battery temperature and it acts to prevent the battery overheating, but does it have the capability to heat a cold battery so that it can handle a higher charge rate?
    To do that, the liquid flowing through the battery pack would need to pass through a heat exchanger, external to the battery pack, to be be either heated or cooled depending on the actual battery temperature. I had presumed the fans were simply blowing cool air over some sort of radiator that the liquid passed through, resulting in the liquid being cooled, but it may be that there is some sort of heater in the system so that the fans can blow warm air over the radiator to heat the liquid.

  • Awesome stuff! Can you do a charge test your car and the 39 at the same to see if they charge at the same rate on the same charger at the same time? This might show the issue is with the charger and not the car.

  • With the HVAC issue, have you tried adjusting the flow balance and direction of the air yourself? If so, that might explain some of the unbalanced air temperatures. I have an Ioniq and used to have that problem. I now just set the temperature and put system in auto mode. I'm toasty warm and the heat arrives much faster than any ice I've driven.

  • While it may be possible to set the car up at home to be nice and cozy from the start, once at work, there are not charging options. The issue you have thrown up regarding the temperature settings are of concern. You may say, forget the dial figure and just turn it to where you are comfortable, but to have 'cold' air blowing through should only work in the summer with a temperature sensor facing the windscreen. It would appear that everybody should test their dream EV car in the winter to ensure that it will perform as they would like.
    There appears to be more questions about people's expectations coming from an ICE environment and being thrown in to an EV option thinking that everything will be the same. At least with an ICE car, you know it will be cold to start with and once the temperature sensor goes out I(Honda Jazz) you will get heat and the temperature gauge will reflect what you need. I would also be interested to learn about the direction of air flow with all the dashboard, screen and footwell settings. Starting from work (with no charging facility) on a cold winter evening, I would expect to have the front screen, overtaking mirror and rear screen defrost buttons pressed and a lot of warm air ultimately being blown out or elements heated to clear everything up for safer driving.
    It still leaves the question about winter driving and impact on range – It is wet, and you need the wipers on. It is cold and you need the heater on. It is frosty and you need the rear screen heater and overtaking mirrors elements on. What range then?
    Great video and opening up some tantalising questions.

  • The throttling may be because of grid issues rather than the car. The UK's infrastructure is creaky (close to collapse if you believe some insiders) and cold days with high daytime grid usage will cause power distribution issues. Best to try this again overnight I'm afraid when grid usage is lower. Clearly not Nissan levels of rapidgate though.

  • The problem with tests like this is the number of variables. You may have used a 50Kw rapid charger but what was the demands on the gird near the charger? Was it a case that the charger was automatically restricting the power because of other demands locally and not the car? Maybe over six months or a year keeping detailed logs an answer may be found but I doubt it because of the number of variables involved. To get the results the manufacture claims you will need to use that charge all manufactures used to do their tests. I understand that it is in a place called Utopia. Good video keep them coming please. I would love to know how much power it would use running at 70mph all the way from Exeter Services on the M5 to the A39 turn off for Truro in Cornwall.

  • I think you’re right here that not knowing fully what the car is doing and not knowing fully what the charger is doing is unhelpful. I recently got 46kW at high 60% SOC on our IONIQ then 30-ish at 40% on the same charger a day later. Lots of variables and not a very transparent end user experience for us, all in all, as you say 🙂

  • What you are seeing here is a cold battery charging issue which is expected, once you warmed it up you got normal charge rates, in a real test you would start out with 100% drive for a least 100 miles heating up the battery and only then rapid charge, does the Kona not have battery temp readout, very poor if it doesn"t.

  • I see you also hilighted my reasons for wanting heated seats in an EV lol. They are essential in the winter in electric cars and a bare minimum expectation on any car over 15k these days.

  • Wow, that seems much more aggressive tapering than I see on the 40 kW leaf. Weird. Re the heating we've found the leaf is the opposite, we need to turn the heating down. Even at around zero degrees outside if we have it any higher than 17 degrees it's too hot. The leaf seems to charge at 45 kW until around 60% charge and them drops down to around 35 kW. It only drops down to the 20s when you get past 70 to 80%. Wonder what's going on.

  • Nigel, nice set of videos comparing the two versions. The in-car heating issue is getting frustrating and will probably get worse as the temperature drops. I may have to report the Hyundai.

  • As you pointed out these kinds of tests are a little tricky because of all the parameters. I wonder if the cooling fans are used to cool the bms. I thought the batteries are liquid cooled but I could be wrong though the fans may push air through a radiator. In any case something like leaf spy would give a better understanding of what’s going on.

  • With a 39kw Kona on order…I’m concerned. We need to understand what is going on here. My first thought is it’s most likely to be to do with temperature. Hyundai need to make more information available about the charging and BMS processes.

Leave a Reply

Your email address will not be published. Required fields are marked *